Was this an inappropriate gift to give?

My girlfriend's sister just turned 30 and I wanted to give her a decent gift but I don't have a lot of cash. She's a big foody. It is her one pion in life. So, I gave her my grandmother's cookbook. This infuriated my girlfriend. I don't get it. My girlfriend is a Financial yst who has about as much pion for food as most Texans have for watching cricket. Was my gift an inappropriate one?